mirror of git://gcc.gnu.org/git/gcc.git
81 lines
3.0 KiB
Java
81 lines
3.0 KiB
Java
/* AbstractSet.java -- Abstract implementation of most of Set
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Copyright (C) 1998 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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As a special exception, if you link this library with other files to
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produce an executable, this library does not by itself cause the
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resulting executable to be covered by the GNU General Public License.
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This exception does not however invalidate any other reasons why the
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executable file might be covered by the GNU General Public License. */
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package java.util;
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/**
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* An abstract implementation of Set to make it easier to create your own
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* implementations. In order to create a Set, subclass AbstractSet and
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* implement the same methods that are required for AbstractCollection
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* (although these methods must of course meet the requirements that Set puts
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* on them - specifically, no element may be in the set more than once). This
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* class simply provides implementations of equals() and hashCode() to fulfil
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* the requirements placed on them by the Set interface.
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*/
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public abstract class AbstractSet extends AbstractCollection implements Set {
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/**
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* Tests whether the given object is equal to this Set. This implementation
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* first checks whether this set <em>is</em> the given object, and returns
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* true if so. Otherwise, if o is a Set and is the same size as this one, it
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* returns the result of calling containsAll on the given Set. Otherwise, it
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* returns false.
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*
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* @param o the Object to be tested for equality with this Set
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* @return true if the given object is equal to this Set
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*/
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public boolean equals(Object o) {
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if (o == this) {
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return true;
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} else if (o instanceof Set && ((Set)o).size() == size()) {
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return containsAll((Collection)o);
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} else {
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return false;
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}
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}
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/**
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* Returns a hash code for this Set. The hash code of a Set is the sum of the
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* hash codes of all its elements, except that the hash code of null is
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* defined to be zero. This implementation obtains an Iterator over the Set,
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* and sums the results.
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*
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* @return a hash code for this Set
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*/
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public int hashCode() {
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int hash = 0;
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Iterator i = iterator();
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while (i.hasNext()) {
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try {
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hash += i.next().hashCode();
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} catch (NullPointerException e) {
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}
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}
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return hash;
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}
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}
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